Method of heat treating rails



Patented Apr. 6, 1937 2,075,983 METHOD or HEAT 'rrma'rme RAILS Harry S. George, Massapequa, N. Y., assignor, by mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York No Drawing. Application September 6, 1933, Serial No. 688,336

7 Claims. 148 2l.5)

This invention relates to heat treated rails An Object y invention is and to a method of heat treating them.

The tread surfaces at the ends of rails at joints 3 the rest of the tread surfaces of rails, because metal when subleeted to service 5 at the ends of rails there is no support against Amthel' Object my invention 18 to Pr vide end flow of rail metal at the tread surfaces an improved method of effectively heat treating thereof; hence, the rate at WhlCh tread surfaces and hardehln! substantially n he same manner of rails become battered is greatest at rail ends tread Surface areas at the ds o a plurality of This lower ng of the running or tread surfaces f rails Wlth asingle application Of heat and Without rails at rail Joints increases the effect of the employing any external q e medium. pressure of rolling trafiic by converting it into a A further ehJeet Of y ion is to provide downward blow as the wheels pass over rail joints. an Improved method of uniformly hardening is action sti11 further increases the rate at tread surfaces at the ends of rails by lyin which the tread surfaces at the ends of rails beheart Indirectly t0 the extreme n ed es and 15 come battered over that" of the rest of the rails comers 80 as to a t n an pproxlmately After a few years of service the amount of batter uhlfelm hardening mp ature over the entire at rail joints becomes so great that it IS necessary treated areasto build up the tread surfaces at the ends of rails Further Objects and advantages ll become 90 t t general level of t rails by depositing apparent as the following description proceeds, metal on the depressed areas and the various features of novelty which charac- It has generally been the practice to harden terize my invention W111 be pointed out par the tread surfaces at the ends of rails by heat tieulality m the claims annexed to and forming treatment, so as to retard the rate of batter a P of this fi a n- Heretofore the only methods of heat treating In accordance with the principles f his inthe tread surfaces at the ends of rails whlch have ventien, the tread surfaces at the s of rails proved pract cable employ an external quenching are rapidly heated to an elevated temperature, medium, such as water or an air blast. In most and then allowed o 0001 haturallyh vat d cases the treatment has included a tempering optemperature 15 sumeiehtly high that h eration Although it is possible to attain the the heated tread surface metal (3015 rapidly: 30 desired results with such methods when great it will 3require adequate degree of har n ss, care 15 employed the methods are very dimcult and throughout the specification and claims this because of the sharp corners at the tread surfaces elevated temperature is termed elevated hardat the ends of rails. Certain precautionary ehihg temperature"- 30 measures are necessary if any success is to be It is t0 he hderstmdthat the expressmh attained in safeguarding against cracks or the 11m] 00011118" signifies the combined 00011118 ect setting up of internal stresses in the tread surfaces of convection and di i n f h at from the rail which, when combined with repeated stresses to the surrounding s he 000 18 ct 01 from service, often result in the eventual cracking the underlying and adjacent mass of rail which 0 of the corners of rail ends. These precautionary s relatively cool. I have found that the latter 40 measures include the very gradual application effect is much greater'than the cooling effect of of heat, especially at the corners of the tread air where a relatively small tread surface area, of surfaces at rail ends. This is especially true an r in rail i h e d Hardenin of the when a secondary tempering operation is emtread surfaces of rails with natural cooling in the 4;, ployed, because of the extra hazard entailed in manner just explained should notbeconfused with the drastic application of heat to steel in a hardthe hardening of self-hardening steel as rail ened state. Heretofore, these precautions have steel generally is not a self-hardening steel not been taken into consideration in heat treatrdinary rails usually contain from approxiing rail ends in track perhaps from ignorance or mately .55 to 80 per cent carbon and a similar or the practical difficulties amount of manganese, and it has been found that 5 encountered As a consequence of the cracking they readily respond to bee. treatment when tendency of the tread surfaces at rail ends and allowed to cool naturally from an elevated hardfor other reasons, the hardening of tread surfaces ening temperature.

at rail ends has In order to produces. substantially uniform not generally proved very successful. and latistectory' condition of hardnea rality of rails having heat treated tread surface I crime: 55

-treated tread surface areas at the ends of rails with natural cooling, it is desirable to control both the temperature to which a tread surface area is heated and the depth of penetration of the heat. This may be accomplished by utilizing a high temperature heat having a substantially constant rate of heat output, and by applying such high temperature heat to tread surface areas at rail ends for a predetermined length of time. This insures the heating of treadsurface areas to an elevated hardening temperature before too much heat has penetrated into the mass of the rail, and also avoids the use of a source of heat of such intensity that only a superficial or skin hardening is effected. After the heat has been applied to a tread surface area for a predetermined length of time, the application of heat is stopped. The underlying mass of the rail will remain relatively cool and exert a quenching effect on the heated tread surface area by withdrawing heat therefrom to cool and uniformly harden it naturally. In this manner the corresponding portions of different tread surface areas are heated substantially uniformly to the same elevated hardening temperature, so that a substantially uniform hardness pattern is produced on a plurality of tread surface areas heat treated.

I prefer to use a high temperature gas flame or flames as the source of heat, and for this purpose employ a suitable burner, such as a blowpipe. The burner may be supplied with a suitable combustible gas, such as a mixture of oxygen and acetylene, at a fixed pressure. By standardizing on a certain size flame and timing the application of the flame on a tread surface area at the end of a rail, a simple method of controlling the heat treating of the tread surfaces at the ends of rails is obtained to produce uniformity of hardness and depth of heat treating. When an oxy-acetylene flame is employed as a source of heat, a strictly neutral flame or a flame having a slight feather of excess acetylene may be used.

The flame is preferably applied to the rail tread surface and moved progressively along the rail head at a substantially predetermined rate of speed, an oscillatory movement back and forth across the rail tread surface being imparted to the flame as it is being advanced along the length of the rail. This progressive movement of the flame may start from a point back from the end of the rail and advance toward the rail end, or the movement of the flame may start from the extreme end of the rail and advance back from the rail end. In certain instances it is preferable to move the flame from the extreme end of the rail toward the center of the rail, for reasons which will be given hereafter.

When the flame is first applied to the tread surface area to be heat treated, only an oscillatory back and forth movement across the rail head is imparted to it for a definite length of time, in order toraise the tread surface metal to the proper elevated hardening temperature at the starting point. After the metal at the starting point has been sufliciently heated, the flame is advanced longitudinally of the rail head at a definite rate of speed. The oscillatory movement imparted to the flame should be such that the strokes across the rail head are substantially transverse to the length of the rail, and end about one-half of an inch inside the lateral edges of the rail head.

' started at a point This insures a progressiveand uniform application of heat in the" and when the flame is moved back from the extreme end of the rail, the application of heat is I near the extreme end edge of the rail. The conduction of heat to the corners of rail tread surfaces from the heated tread surface portions adjacent thereto is suflicient to raise the corners to the same elevated hardening temperature as the remainder of the heat treated areas.

Although the tread surface of a single rail end may be heat treated alone, it is preferable to heat treat simultaneously the tread surface areas at both ends of abutting rails at a rail joint. In so doing, it is desirable that the application of heat takes place simultaneously at the extreme ends of the rail tread surfaces so as to produce substantially uniform hardening of the tread surfaces at both ra' ends. When the tread surface areas to be heat treated are of substantially the same length it is possible for two operators to start applying heat on the rails at points back from the extreme ends of the rail heads, and to finish the heat treating operation at substantially the same time. In such instances there is no danger of one rail receiving heat from an abuttingrail and thereby retarding its rate of natural cooling. When the tread surface areas to be heat treated at a rail joint are of different lengths, however, it is more diflicult for each operator to start applying heat on the tread surfaces at the proper time at points back from ends of the respective rails, so that they will finish the heat treating operation at about the same time at the extreme ends of the rails. Further, when simultaneously applying heat progressively toward the ends of abutting rails at a rail joint, there sometimes is the likelihood of overheating the corners of the tread surfaces at the extreme ends of the rails. This tends to delay the rate of natural cooling and to permit the rest of the rail to absorb toomuch heat.

In applying the heat initially on the tread surfaces at a point near the extreme ends of the rails and progressively moving the sources of heat toward the centers of the abutting rails, the danger of overheating the corners and extreme ends of .the tread surfaces of the rails is reduced considerably. Further, the tread surfaces at the ends of abutting rails are always heated simultaneously even in instances where the areas to be heat treated are of different lengths. Thus, no-additional duty is imposed on an operator heat treating the shorter tread surface area as to the exact time he should start applying heat, as is the case when the sources of heat are progressively moved toward the ends of the rail heads.

The above-described manner of heat-treating rail tread surfaces with natural cooling is applicable to rails which have not been built up and which will be referred to as new rails, and to rails which have been built-up. In new rails, if too long a tread surface area of the full width of a rail is heated, some sacrifice in hardening must be expected on the extreme comer of the tread surlong are heated progressively and with sumcient rapidity to insure effective natural cooling.

s In heat treating tread surface areas at the ends of built-up rails,

inches in length, areas at a rail joint may vary considerably in length because of the manner in which traffic moves over a section of track. For example, where the traflic is one-way or uni-directional, the tread surface at the end of the receiving rail usually is worn to a greater extent than the tread surface at the end of the leaving rail. In heat treating the tread surfaces of built-up rails, the application of heat can be extended about inch beyond the end of the metal deposit, and still a satisfactory hardness can be attained.

Examples of rail ends having tread surface areas satisfactorily hardened in accordance with the method described above will be listed:

Example 1.A tread surface area 2 inches long No- 30 tip having the oxygen pressure being about lbs. per square inch. The flame was adjusted to a slight feather of excess acetylene and applied on the tread surface at a point 1% inches from the end of the rail head at a slight inclination towards the rail end, and with the tip of the inner cone about $4;

inch above the tread surface. For the first 45 p from the extreme seconds only an oscillatory movement back ,and forth across the rail head was imparted to the flame, the number of strokes being between 40 to 60 per minute; This brought the tread surface of the rail to an elevated hardening temperature of about 1600 F. The flame was then advanced toward the end of the rail head at a rate of 15 seconds per inch, and withdrawn before reaching the extreme end of the rail so as to avoid overheating the extreme edge and corners of the rail tread surface. The total time of treatment was 1 minute and 5 seconds. and sufficiently rapid to produce adequate hardness of the rail tread surface with natural cooling.

Example 2.Same as Example 1, except that two flames were used to heat simultaneously tread surfaces at the ends of abutting rails at a rail joint. Both flames were applied on the tread surfaces and withdrawn therefrom at the same time.- Substantially the same results were obtained when the flames were advanced toward or away ends of the rail heads. Example 3..An end tread-surface area 6 inches long having a taperedmetallic deposit 5 inches long was hardened to a, depth of about A; inch in a built-up rail weighing approximately 130 lbs. per linear yard, the. rail end not being at a joint. The composition of the metal deposited in this instance was a steelalloy containing about .50%

snow on red hot rail tread carbon, 0.90% chromium,

manganese, 0.90%

.40 silicon and the remainder iron. A flame similar to that mentioned in Example 1 was used and tread surface. Example 4.End tread surface seconds, were advanced longitudinally of the rails. Each flame was withdrawn after it had reached a point inch beyond the metal deposit on each of rail tread surfaces being heated. Natural cooling effectively produced adequate hardness of the tread surface areas treated.

In hardening the tread surfaces at rail ends with a single application of heat with subsequent natural cooling, the effect of high or low atmospheric and rail temperature will not be very great. If the temperature is as high as F. or as low as 20 F. below zero, the starting time may be increased or decreased by about 5 seconds. differences in atmospheric temperature will not substantially affect the subsequent time of heat treatment because, after the initial 40 to 50 ends, the rail end to all practical purposes is as warm in one instance as in another.

It is preferable that natural cooling alone be reliedupon to or a snow falling are not objectionable, but the di-: rect application of a stream of water or of much surfaces is liable to introduce objectionable non-uniformities in the heat treated area.

By allowing the heated tread surfaces of rail to cool may be applied automatically or semi-automatically on the rail tread surfaces, without departing from the spirit and scope of my invention.

I claim Such.

4- duction from the heated tread surface portions adjacent thereto, controlling the application of heat on each tread surface area by applying the heat for a definite length of time and with such 5 distribution as to heat each tread surface area rapidly to a considerable depth with different portions thereof heated to a substantially uniform elevated hardening temperature, and permitting each heated rail to cool naturally in the atmosphere, the rate of heating being such that natural cooling is effective to harden the heated tread surface areas substantially to the same desired value of hardness.

2. The method of heat treating tread surface areas of similar composition at the ends of a plurality of rails of like size, which comprises applying a source of high temperature heat having a constant rate of heat output at a point near one end of each tread surface area and oscillating $0 the sametransversely back and forth across the rail tread surface, moving said source of high temperature heat longitudinally of the rail, while oscillating the same, to heat successive portions of the tread surface area, the extreme corners of 25 the rail tread surface being heated by conduction of heat from the heated portions adjacent thereto, the application of heat on each tread surface area being controlled by applying the heat for a definite length of time and with such distribution 30 as to heat the tread surface area rapidly to a considerable depth with different portions thereof heated to a substantially uniform elevated hardening temperature, and permitting each rail to cool naturally in the atmosphere, the rate of 35 heating beingsuch that natural cooling is effective to harden the heated tread surface areas substantially to the same desired value of hardness.

3. The method of substantially uniformly heat 40 treating the tread surface areas at the ends of a plurality of built-up rails of like size with the ends of the tread surfaces having metal of similar composition deposited thereon, such heat treated areas extending beyond the metal deposit which comprises applying on each tread surface area except at the extreme corners of the rail tread surface a high temperature source of heat having a substantially constant rate of heat output, the

extreme corners of each rail tread surface receiv- 0 ing heat by conduction from the heated tread surface portions adjacent thereto, controlling the ap plication of heat on each tread surface area by applying the heat for a definite length of time and with such distribution as to heat each tread sur- 85 face area rapidly to a considerable depth with different portions thereof heated to a substantially uniform elevated hardening temperature, and permitting each heated rail to cool naturally in the atmosphere, the rate of heating being such that natural cooling is effective to harden the heat-" ed tread surface areas whereby the hardened areas produced possess substantially the same structural and physical characteristics.-

4. In the method of simultaneously heat treating adjacent tread surface areas at the ends of abutting rails of rail joints in a section-of track, such tread surface areas being of similar composition and the rails being of like size, which includes the steps of applying on each of said tread surface areas at the ends of abutting rails except at the extreme corners of such tread surface areas a high temperature source of heat having a substantially constant rate of heat output, the extreme corners of each rail tread surface receiving heat by conduction from the heated tread surface portions adjacent thereto, and controlling the application of heat by applying the heat on the tread surface areas for a definite similar length of time and with such distribution that corresponding portions of different areas are heated substantially uniformly to the same elevated hardening temperature, adjacent areas at each rail joint being heated in such a manner that the portions of the areas adjacent to the extreme ends of the abutting rails are heated substantially at the same time.

5. The method of surface hardening tread surface areas of rails which comprises applying to each tread surface area, except at the extreme corners thereof, a localized high temperature heating medium having a substantially constant rate of heat output, the extreme corners of each rail tread surface receiving heat by conduction from the heated tread surface portions adjacent thereto, and cooling the heated area at a rate sufficient to harden the same.

6. A method of hardening a surface of a ferrous metal body, such surface being bounded by corners, such method comprising applying a high temperature heating medium directly to all portions of said surface except to those portions closely adjacent said corners, so as to heat only by conduction said portions closely adjacent said corners and to directly heat the remaining portions of said surface; and cooling the so heated surface at a rate sufficient to harden the same.

'7. A method of hardening a surface of a ferrous metal body which comprises applying a high temperature heating medium directly to all portions of said surface except to those portions closely adjacent the boundaries of said surface, so as to heat only by conduction said portions adjacent said boundaries and to directly-heat the remaining portions of said surface; and cooling the so heated surface at a rate suflicient to harden the same.

HARRY S. GEORGE. 

